1. Field of the Invention
The present invention relates generally to the fields of polygraphs and lie detection. More specifically, the present invention relates to a method of lie detection utilizing electrogastrography.
2. Description of the Related Art
Lie detection by objective means is desired in several circumstances including criminal investigations and pre-employment screening for high-security positions. Additionally, many government entities and some private-sector employers may require or may ask potential employees to undergo a polygraph exam prior to employment. Currently, this is accomplished by a polygraph examination that utilizes a polygraph instrument that collects physiological data from at least three systems in the human body. A polygraph instrument detects involuntary physiological responses going on in a person's body when that person is subjected to stress, including the stress of deception. Responses monitored during a polygraph examination, traditionally including heart rate, blood pressure, respiratory rate and electrodermal activity, e.g., the galvanic skin response which can be measured in the sweatiness of a fingertip, change in comparison to normal levels.
Most polygraph tests are of the CQT variety in which deception is determined by comparing physiological responses to relevant questions to a baseline determined by control questions. A typical polygraph examination a pre-test phase, a chart collection phase and a test data analysis phase. In the pre-test, the polygraph examiner completes required paperwork and talks with the examinee about the test. The examiner discusses the questions to be asked and familiarizes the examinee with the testing procedure. During the chart collection phase, the examiner administers and collects a number of polygraph charts. The examiner subsequently analyzes the charts and renders his opinion as to the truthfulness of the person taking the test. When appropriate, the examiner may offer the examinee an opportunity to explain physiological responses in relation to one or more questions asked during the test.
A system for lie detection is only as good as its ability to discriminate between the stress of deception or lying and the simple stress engendered by the polygraph examination itself. Thus, when the Examiner administers the relevant questions, the fact that the examinee is being questioned, that is, the actual polygraph examination has commenced, may be sufficient to elevate anxiety levels in the examinee from baseline even when the examinee is responding truthfully. Additionally, artificially inflated baseline values to control questions may be acquired when the examinee employs physical or mental countermeasures to beat the polygraph. In this instance deceptive response may score even with or lower than baseline.
Electrogastrography describes the recording and interpretation of electrical activity of the stomach. Recordings can be made from the gastrointestinal mucosa, serosa, or skin surface. Because of its ease of use, cutaneous EGG is used most frequently. The electrical activity of the stomach can be subdivided into two general categories: electrical control activity (ECA) and electrical response activity (ERA). Electrical control activity is characterized by regularly recurring electrical potentials, originating in the gastric pacemaker located in the corpus of the stomach and sweeping in an annular band with increasing velocity toward the pylorus. Electrical control activity is not associated with contractions of the stomach unless coupled with action potentials, referred to as electrical response activity.
There is a recognized need in the art for improvements in systems and methods for lie detection. Specifically, the prior art is deficient in devices and methods that measure the gastric electrical rhythm as a parameter in lie detection. The present invention fulfills this long-standing need and desire in the art.